No abstract

Exotic ambrosia beetles (Curculionidae: Scolytinae) in the tribe Xyleborini include destructive pests of trees growing in horticultural cropping systems. Three species are especially problematic: Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky), and Xylosandrus germanus (Blandford). Due to similarities in their host tree interactions, this mini-review focuses on these three species with the goal of describing their host-selection behaviour, characterising associated semiochemicals, and assessing how these interactions relate to their management. All three of these Xylosandrus spp. attack a broad range of trees and shrubs. Physiologically stressed trees are preferentially attacked by X. crassiusculus and X. germanus, but the influence of stress on host selection by X. compactus is less clear. Ethanol is emitted from weakened trees in response to a variety of stressors, and it represents an important attractant for all three species. Other host-derived compounds tested are inconsistent or inactive. Verbenone inhibits attraction to ethanol, but the effect is inconsistent and does not prevent attacks. Integrating repellents and attractants into a push–pull management strategy has been ineffective for reducing attacks but could be optimised further. Overall, maintaining host vigour and minimising stress-induced ethanol are keys for managing these insects, particularly X. crassiusculus and X. germanus.

1 Ethanol acts as an attractant that aids Xylosandrus germanus (Blandford) in locating living but weakened hosts. Electroantennogram (EAG) and field trapping experiments were conducted with conophthorin and other selected semiochemicals that function as important olfactory cues for various ambrosia beetles to characterize their effect on the attraction of X. germanus to ethanol and to assess whether EAG responses provide an indication of behavioural activity. Thus, semiochemicals hypothesized to enhance (i.e. conophthorin), reduce (i.e. terpinolene, verbenone) or have a negligible (i.e. lineatin, sulcatol, retusol) effect on the attraction of X. germanus to ethanol were selected for comparative purposes. 2 Ethanol plus conophthorin elicited larger EAG amplitudes than binary (1 : 1) mixtures of ethanol plus the remaining semiochemicals at dilutions of 0.001%, 0.01% and 1% per compound. Conophthorin also enhanced the attraction of X. germanus, Euwallacea validus (Eichhoff) and Cyclorhipidion pelliculosum (Eichhoff) to ethanol under field conditions. By contrast, terpinolene and verbenone reduced the attraction of X. germanus and other ambrosia beetles to ethanol. 3 Semiochemicals that enhance (i.e. conophthorin) or reduce (i.e. terpinolene, verbenone) attraction by X. germanus may improve monitoring and/or management tactics. These results also suggest that EAG responses can indicate field behavioural activity and be useful for screening attractants for X. germanus.

BACKGROUND: The flatheaded appletree borer (Chrysobothris femorata Olivier) (FHAB) is a native pest of fruit, shade and nut trees throughout the United States. Use of cover crops is an effective pest management tool for some key insect pests in vegetable and cereal production systems, but its impact in woody ornamental production systems has not been investigated. The goal of this study was to evaluate the effectiveness of a winter cover crop for management of FHAB in nursery production. Red maple trees (Acer rubrum L.) grown under four treatment regimes (cover crop, cover crop + insecticide, bare row and bare row + insecticide) were evaluated for damage by FHAB and impact on tree growth parameters. RESULTS:The cover crop reduced FHAB damage, with results equivalent to standard imidacloprid treatments. The reduction in FHAB attacks in cover crop treatments may be due to microclimate changes at preferred oviposition sites, trunk camouflage or interference with access to oviposition sites. Tree growth was reduced in the cover crop treatments due to competition for resources. CONCLUSION: Physical blockage of oviposition sites by cover crops and subsequent microclimate changes protected against FHAB damage. Therefore, cover crops can be an alternative to chemical insecticides.